Running-linked sound producing device

ABSTRACT

A running-linked sound producing device produces a running-linked sound according to a running state of a vehicle. The running-linked sound producing device includes a vehicle speed estimation unit to estimate a vehicle speed of the vehicle, an accelerator command value estimation unit to estimate an accelerator command value based on a vehicle speed estimated by the vehicle speed estimation unit, and a running-linked sound generation unit that generates a running-linked sound, wherein the running-linked sound generation unit generates a running-linked sound based on a vehicle speed estimated by the vehicle speed estimation unit and an accelerator command value estimated by the accelerator command value estimation unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a running-linked sound producing devicefor producing a running-linked sound according to the running state of avehicle.

2. Description of the Related Art

Recent noise regulations have led to many improvements in a reduction inengine sounds of vehicles, and at present, engines that have been madeconsiderably silent have been put into practical use. Moreover, invehicles, such as hybrid vehicles and electric vehicles that are poweredby electric motors, sounds produced by the power sources are smallparticularly during low-speed running. In some cases, such extremelyquiet vehicles are hardly noticed by pedestrians, etc. Moreover, forvehicle passengers also, the sounds heard from the driving sources areminimal, and the sound quality is not always excellent. Therefore, theenjoyment in driving may be reduced.

Japanese Unexamined Patent Application Publication No. 2000-1142discloses a simulated engine sound producing device for a vehicle thatproduces a simulated engine sound corresponding to a vehicle operationstate based on signals from sensors provided on the vehicle.

The prior art of Japanese Unexamined Patent Application Publication No.2000-1142 has a configuration that obtains signals from sensors providedon a vehicle, and thus requires a large number of wirings. Therefore,not only is the structure complicated, but the number of fitting stepsis also increased, and it is inevitable that the cost is accordinglyincreased.

SUMMARY OF THE INVENTION

A preferred embodiment of the present invention provides arunning-linked sound producing device which has a simple configurationand is also easily fitted to a vehicle.

More specifically, a preferred embodiment of the present inventionprovides a running-linked sound producing device for producing arunning-linked sound according to a running state of a vehicle,including a vehicle speed estimating unit programmed to estimate avehicle speed of the vehicle, an accelerator command value estimatingunit programmed to estimate an accelerator command value based on thevehicle speed estimated by the vehicle speed estimating unit, and arunning-linked sound generating unit programmed to generate arunning-linked sound based on the vehicle speed estimated by the vehiclespeed estimating unit and the accelerator command value estimated by theaccelerator command value estimating unit.

In this device, a vehicle speed of the vehicle is determined byestimation, so that no sensor (vehicle speed sensor) to directly detecta vehicle speed is required. Therefore, because it is not necessary toobtain a signal from a vehicle speed sensor provided on the vehicle, awiring therefor is not required. Further, because an accelerator commandvalue is also estimated based on the estimated vehicle speed, a wiringto obtain an accelerator command value from the vehicle is also notrequired. As a result, wirings can be reduced, the configuration can besimplified accordingly, and fitting to the vehicle also becomes easy.Furthermore, a running-linked sound according to the estimated vehiclespeed and estimated accelerator command value is generated, so that anappropriate running-linked sound according to the running state of thevehicle can be produced.

In a preferred embodiment of the present invention, the acceleratorcommand value estimating unit includes a torque estimating unitprogrammed to estimate a producing torque of a motor of the vehiclebased on the vehicle speed estimated by the vehicle speed estimatingunit, and to estimate the accelerator command value according to theestimated producing torque. In this arrangement, the producing torque ofa motor is estimated according to the estimated vehicle speed, so thatit is not necessary to obtain information to estimate the producingtorque from the vehicle. Then, because an accelerator command value isestimated according to the estimated producing torque, the acceleratorcommand value can be accurately estimated. That is, an output of themotor is estimated from the vehicle speed, and an accelerator commandvalue to produce the output is estimated.

The torque estimating unit may include a running resistance computingunit programmed to compute a running resistance of the vehicle, and anecessary torque computing unit programmed to compute a necessary torquethat needs to be produced by the motor in order to the vehicle run basedon the running resistance computed by the running resistance computingunit. In this case, the accelerator command value estimating unit may beprogrammed to estimate the accelerator command value based on thenecessary torque computed by the necessary torque computing unit and amotor rotation speed.

According to this arrangement, the necessary torque that needs to beproduced by the motor is determined based on the running resistance ofthe vehicle, and the accelerator command value is estimated based on thenecessary torque and the motor rotation speed. As a result, theaccelerator command value can be more accurately estimated, so that arunning-linked sound matching the running state of the vehicle can beproduced.

In a preferred embodiment of the present invention, the running-linkedsound producing device further includes an acceleration computing unitprogrammed to estimate an acceleration of the vehicle, and a gradientestimating unit programmed to estimate a gradient of a road surface onwhich the vehicle is running, and the necessary torque computing unit isprogrammed to compute the necessary torque based on the runningresistance computed by the running resistance computing unit, theacceleration estimated by the acceleration computing unit, and the roadsurface gradient estimated by the gradient estimating unit.

According to this arrangement, the acceleration of a vehicle and theroad surface gradient are estimated. Then, the necessary torque iscomputed based on the estimated acceleration and the road surfacegradient besides the running resistance, and the accelerator commandvalue is estimated using the necessary torque. Therefore, theaccelerator command value can be more accurately estimated, so that arunning-linked sound reflecting the running state of the vehicle can beproduced more accurately.

In a preferred embodiment of the present invention, the acceleratorcommand value estimating unit includes a producing torque ratiocomputing unit programmed to compute a producing torque ratio that is aratio of the necessary torque to a maximum torque that can be producedby the motor at the motor rotation speed, wherein the acceleratorcommand value estimating unit is programmed to estimate the acceleratorcommand value based on the producing torque ratio computed by theproducing torque ratio computing unit.

According to this arrangement, the accelerator command value isestimated according to the producing torque ratio, so that theaccelerator command value can be more appropriately estimated.Accordingly, a running-linked sound reflecting the running state of thevehicle can be produced more accurately.

In this case, it is preferable to further include a motor characteristicchanging unit programmed to change characteristics of the maximum torquewith respect to the motor rotation speed. As a result, an operation forproducing a running-linked sound can be tuned according tocharacteristics of the motor provided on the vehicle and userpreference.

Moreover, it is preferable to further include an acceleratorcharacteristic changing unit programmed to change characteristics of theaccelerator command value with respect to the producing torque ratio.Also as a result, an operation for producing a running-linked sound canbe tuned according to characteristics of the motor provided on thevehicle and user preference.

It is preferable that the vehicle speed estimating unit is programmed soas to estimate the vehicle speed using an output signal of a sensorprovided in the running-linked sound producing device. As a result, thevehicle speed can be estimated without obtaining information from thevehicle, so that the configuration of wirings and the like can besimplified, and fitting work of the device can be simplifiedaccordingly.

For example, the sensor may include an acceleration sensor, and thevehicle speed estimating unit may be programmed to integrate anacceleration detected by the acceleration sensor to estimate the vehiclespeed. As a result, the vehicle speed can be estimated even withoutusing a vehicle speed sensor, so that the configuration is simplified.

In a preferred embodiment of the present invention, the running-linkedsound producing device further includes a gradient estimating unitprogrammed to estimate a gradient of a road surface on which the vehicleis running, and the vehicle speed estimating unit is programmed tocorrect an acceleration detected by the acceleration sensor according tothe road surface gradient estimated by the gradient estimating unit, andto integrate the corrected acceleration to estimate the vehicle speed.This arrangement, when an acceleration of gravity has an influence on anoutput of the acceleration sensor due to the road surface gradient,allows determining an acceleration of the vehicle thereby minimizing oreliminating the influence of gravity. As a result, an estimated vehiclespeed based on the acceleration can be accurately performed, so that arunning-linked sound matching the running state of the vehicle can beproduced.

In a preferred embodiment of the present invention, the sensor includesan angular rate sensor, and the gradient estimating unit is programmedto integrate an angular rate detected by the angular rate sensor, and toestimate the road surface gradient. This arrangement allows determiningthe road surface gradient without providing a sensor to directly detectthe road surface gradient. As a result, a running state of the vehiclereflecting the road surface gradient can be determined with a simpleconfiguration, and accordingly, a running-linked sound matching therunning state of the vehicle can be produced.

In a preferred embodiment of the present invention, the sensor includesa GPS (Global Positioning System) receiver, and the vehicle speedestimating unit is programmed to estimate the vehicle speed based on anoutput signal (for example, position data, moving speed data, and thelike) of the GPS receiver. This arrangement also allows estimating thevehicle speed without obtaining information from the vehicle. As aresult, a running-linked sound producing device that can be equipped onthe vehicle at a low cost can be provided.

In a preferred embodiment of the present invention, the running-linkedsound generating unit includes a motor rotation speed estimating unitprogrammed to estimate a motor rotation speed based on the vehicle speedestimated by the vehicle speed estimating unit, and to generate arunning-linked sound based on the estimated accelerator command valueand the motor rotation speed. According to this arrangement, the motorrotation speed is estimated based on the vehicle speed estimated by thevehicle speed estimating unit. Therefore, it is not necessary to obtaininformation concerning the motor rotation speed from the vehicle body,so that a running-linked sound producing device can be equipped on thevehicle at a low cost, and a running-linked sound that is appropriatelylinked to the running state can be provided.

For example, in a vehicle that transmits motor revolutions to a runningwheel at a constant reduction ratio, the motor rotation speed can beestimated based on the vehicle speed, the reduction ratio, and adiameter of the running wheel.

In a preferred embodiment of the present invention, the running-linkedsound generating unit includes a motor rotation speed estimating unitprogrammed to estimate a motor rotation speed based on the vehicle speedestimated by the vehicle speed estimating unit and the acceleratorcommand value estimated by the accelerator command value estimatingunit, and is programmed to generate a running-linked sound based on theestimated accelerator command value and the motor rotation speed.According to this arrangement, the motor rotation speed is estimatedbased on the estimated vehicle speed and the accelerator command value.Therefore, it is not necessary to obtain information concerning themotor rotation speed from the vehicle body, so that a running-linkedsound producing device can be equipped on the vehicle at a low cost, anda running-linked sound that is appropriately linked to the running statecan be provided. Even when a ratio of motor revolutions and runningwheel revolutions fluctuates according to the accelerator command value,the motor rotation speed can be accurately estimated. As a result, arunning-linked sound matching the running state of the vehicle can beproduced with a simple configuration.

The motor may be an electric motor or may be an engine (internalcombustion engine). In most cases in which an electric motor is used asa power source, revolutions of the electric motor are reduced at aconstant reduction ratio and transmitted to the running wheel. Vehiclesusing engines as their power sources usually include transmissions, sothat in such vehicles, the ratio (reduction ratio) of engine revolutionsand running wheel revolutions is generally dependent on not only avehicle speed but also an accelerator command value. Even when a motoractually mounted on a vehicle is an electric motor, an engine may beregarded as a virtual motor to estimate its rotation speed. That is, the“motor rotation speed” may be a rotation speed of a real motor or may bea rotation speed of a virtual motor.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view showing a vehicle mounted with arunning-linked sound producing device according to a preferredembodiment of the present invention.

FIG. 2 is a block diagram for explaining an electrical configuration ofthe running-linked sound producing device.

FIG. 3 is a block diagram for explaining a configuration example of avehicle speed estimation unit.

FIG. 4 is an explanatory view showing forces that act on an electrictwo-wheeled vehicle on an inclined road surface.

FIG. 5 is a flowchart showing the content of processing by the vehiclespeed estimation unit.

FIG. 6 is a block diagram for explaining a configuration example of anaccelerator command value estimation unit.

FIG. 7 shows an example of a maximum torque map representing therelationship between the motor rotation speed and maximum torque.

FIG. 8 shows an example of an accelerator opening degree maprepresenting the relationship of the estimated accelerator openingdegree with respect to the producing torque ratio.

FIG. 9 is a flowchart showing a processing by the accelerator commandvalue estimation unit.

FIG. 10 is a block diagram showing a configuration example of arunning-linked sound generation unit.

FIG. 11A shows an example of a virtual engine speed map.

FIG. 11B shows a constant engine speed line when an electric two-wheeledvehicle is accelerating in a state with a relatively small value of theaccelerator opening degree.

FIG. 11C shows a constant engine speed line when an electric two-wheeledvehicle is accelerating in a state with a relatively large acceleratoropening degree.

FIG. 11D shows an operation when the vehicle acceleration has changedfrom a positive value to a negative value in determination of a virtualengine speed in accordance with a constant engine speed line.

FIG. 11E shows an operation when the vehicle acceleration has changedfrom a positive value to a negative value in determination of a virtualengine speed in accordance with a constant engine speed line.

FIG. 11F shows behavior when the vehicle acceleration has once changedto a negative value, and then changed to a positive value.

FIG. 12 is a view for explaining a configuration example of an ordersound gain generation unit.

FIG. 13 is a view for explaining a configuration example of a randomsound gain generation unit.

FIG. 14A is a view for explaining changes in order sound data accordingto the accelerator opening degree and virtual engine speed.

FIG. 14B is a view for explaining changes in random sound data accordingto the accelerator opening degree and virtual engine speed.

FIG. 15 shows an example where order sound data was reproduced andfrequency-analyzed.

FIG. 16A is a view for explaining a running-linked sound producingdevice according to another preferred embodiment of the presentinvention, showing vehicle speed estimation using position data outputby a GPS receiver.

FIG. 16B is a flowchart for explaining an example of vehicle speedestimation using position data output by a GPS receiver.

FIG. 17 is a flowchart for explaining a running-linked sound producingdevice according to still another preferred embodiment of the presentinvention, showing an example of vehicle speed estimation using movingspeed data output by a GPS receiver.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a schematic side view showing a vehicle mounted with arunning-linked sound producing device according to a preferredembodiment of the present invention. The vehicle is, for example, anelectric two-wheeled vehicle 1. More specifically, the electrictwo-wheeled vehicle 1 preferably is a scooter-type electric two-wheeledvehicle, and includes a vehicle body frame 2, a front wheel 3, a rearwheel 4, an electric motor 5, a battery 6, and a vehicle body cover 7,for example. The electric two-wheeled vehicle 1 is arranged to drive theelectric motor 5 by electricity supplied from the battery 6 and drivethe rear wheel 4 serving as a driven wheel by an output of the electricmotor 5.

Into a head pipe 8 disposed on an upper front portion of the vehiclebody frame 2, a steering shaft 9 is freely rotatably inserted. At alower end portion of the steering shaft 9, a pair of left and rightfront forks 10 are attached. The front wheel 3 is attached to the frontforks 10. At an upper end portion of the steering shaft 9, a handle 11is attached. A rider can turn the steering shaft 9, the front forks 10,and the front wheel 3 about the axis of the steering shaft 9 byoperating the handle 11.

At both left and right end portions of the handle 11, grips 12 areprovided, respectively (only the left grip is shown). The right grip isan accelerator grip (accelerator operator). The rider can adjust theoutput of the electric motor 5 by turning the accelerator grip.

The vehicle body frame 2 extends rearward from the head pipe 8. Thevehicle body frame 2 includes a down tube 19 and a pair of left andright frame main bodies 20 disposed behind the down tube 19. The downtube 19 extends obliquely rearward and downward from a lower portion ofthe head pipe 8. The frame main bodies 20 each have a substantiallyS-shape in a side view, extend rearward from a lower end portion of thedown tube 19, run obliquely upward to extend further rearward, and thenextend rearward substantially horizontally.

The vehicle body cover 7 is attached to the vehicle body frame 2. Thevehicle body cover 7 includes a front cover 25 that covers the head pipe8, a lower cover 26 that extends rearward from a lower portion of thefront cover 25, and a rear cover 27 disposed behind the front cover 25.The front cover 25 surrounds a portion of the steering shaft 9 and thehead pipe 8, and surrounds the down tube 19. The lower cover 26 extendsrearward from a lower portion of the front cover 25, and covers aportion of the frame main bodies 20 downward from both the left andright sides. At an upper surface of the lower cover 26, a footrestportion 28 is disposed. The footrest portion 28 is provided for a riderto place his/her feet, and is substantially flat. The rear cover 27 as awhole has a shape extending obliquely rearward and upward from a rearportion of the lower cover 26. The rear cover 27 covers a portion of theframe main bodies 20 from the front and both the left and right sides.

A seat 29 for a rider to sit is attached to an upper portion of theframe main bodies 20. Below the seat 29, an accommodating space isprovided between the left and right pair of frame main bodies 20. In theaccommodating space, a battery 6 serving as a power supply of theelectric motor 5 is disposed. The battery 6 is a rechargeable secondarybattery.

The running-linked sound producing device 30 includes a device main body31 and a speaker 32. In the example of FIG. 1, the device main body 31is disposed below the seat 29 and attached to the frame main bodies 20.The speaker 32 is attached to, for example, the head pipe 8. The devicemain body 31 and the speaker 32 are connected by a wiring 33. The wiring33 is routed inside the vehicle body cover 7, and transfers an audiosignal produced by the device main body 31 to the speaker 32.

FIG. 2 is a block diagram for explaining an electrical configuration ofthe running-linked sound producing device 30. The device main body 31 isconnected to the battery 6 of the electric two-wheeled vehicle 1 via apower supply wiring, and is configured so as to operate by beingsupplied with electricity from the battery 6. Of course, a configurationmay be used in which the device main body 31 includes a built-inbattery, and the device main body 31 operates by the built-in battery.

The device main body 31 includes a sound synthesizer circuit 35, anamplifier 36, and sensors 40. The sensors 40 are provided in a case ofthe device main body 31.

The sensors 40, in the present preferred embodiment, include anacceleration sensor 41 and an angular rate sensor 42 (gyro sensor). Theacceleration sensor 41 may be a 3-axis acceleration sensor that isarranged to detect and output acceleration along the directions of threeorthogonal axes (x-axis, y-axis, z-axis). In the present preferredembodiment, the x-axis of the acceleration sensor 41 matches thefore-and-aft direction of the electric two-wheeled vehicle 1, the y-axisthereof matches the left-right direction of the electric two-wheeledvehicle 1, and the z-axis thereof matches the up-down direction of theelectric two-wheeled vehicle 1. That is, the device main body 31 isattached to the vehicle body frame 2 so as to have such a positionalrelationship. The angular rate sensor 42 is arranged to detect angularrates (roll angular rate, pitch angular rate, and yaw angular rate)about three axes (x-axis, y-axis, and z-axis), respectively. In thepresent preferred embodiment, the x-axis, y-axis, and z-axis of theangular rate sensor 42 are coincident with the x-axis, y-axis, andz-axis of the acceleration sensor 41, respectively. That is, theacceleration sensor 41 and the angular rate sensor 42 are fitted to thecase of the device main body 31 so as to have such a positionalrelationship. Therefore, the x-axis of the angular rate sensor 42matches the fore-and-aft direction of the electric two-wheeled vehicle1, the y-axis thereof matches the left-right direction of the electrictwo-wheeled vehicle 1, and the z-axis thereof matches the up-downdirection of the electric two-wheeled vehicle 1.

The sound synthesizer circuit 35 estimates a running state of theelectric two-wheeled vehicle 1 based on output signals of the sensors40, and generates an audio signal representing a running-linked soundaccording to the estimated running state. The audio signal is amplifiedby the amplifier 36, and the amplified audio signal is provided to thespeaker 32 via the wiring 33. As a result, the speaker 32 is driven toproduce a running-linked sound. The running-linked sound is produced forpeople around the electric two-wheeled vehicle 1, and is also heard bythe rider. The sound synthesizer circuit 35 is preferably programmed togenerate a running-linked sound signal using output signals of only thesensors 40 included in the device main body 31, and is not arranged tobe input with signals from sensors provided on the electric two-wheeledvehicle 1 (outside the running-linked sound producing device 30).

The sensors 40 in the device main body 31 may include a GPS (GlobalPositioning System) receiver 45 (shown by an alternate long and twoshort dashed line), besides the acceleration sensor 41 and the angularrate sensor 42. The GPS receiver 45 is a device that receives signalsfrom a GPS satellite orbiting the earth and generates position data andthe like.

The sound synthesizer circuit 35 includes a microcomputer, and includesa plurality of functional processing units to be realized by arithmeticprocessing performed by the microcomputer. More specifically, the soundsynthesizer circuit 35 includes a vehicle speed estimation unit 37, anaccelerator command value estimation unit 38, and a running-linked soundgeneration unit 39. The vehicle speed estimation unit 37 estimates avehicle speed of the electric two-wheeled vehicle 1 based on outputsignals of the sensors 40. That is, the vehicle speed estimation unit 37estimates a vehicle speed of the electric two-wheeled vehicle 1 withoutusing signals from other sensors equipped on the electric two-wheeledvehicle 1. The accelerator command value estimation unit 38 estimates anaccelerator command value based on the vehicle speed estimated by thevehicle speed estimation unit 37 and output signals of the sensors 40.The accelerator command value corresponds to the operation amount of theaccelerator grip provided on the handle 11. However, it is not necessarythat the estimated accelerator command value accurately corresponds tothe operation amount of the accelerator grip. The accelerator commandvalue estimation unit 38 estimates an accelerator command value withoutusing output signals of other sensors (for example, an accelerator gripoperation amount sensor) provided on the electric two-wheeled vehicle 1.The running-linked sound generation unit 39 generates a running-linkedsound signal based on the vehicle speed estimated by the vehicle speedestimation unit 37 and the accelerator command value estimated by theaccelerator command value estimation unit 38.

FIG. 3 is a block diagram for explaining a more detailed configurationexample of the vehicle speed estimation unit 37. The vehicle speedestimation unit 37 includes a road surface gradient estimation unit 50,a vehicle acceleration calculation unit 54, and a vehicle speedcalculation unit 55. The road surface gradient estimation unit 50includes a gradient estimating unit programmed to estimate a gradient ofa road surface on which the electric two-wheeled vehicle 1 is running,and includes an initial road surface gradient angle calculation unit 51and a road surface gradient angle calculation unit 52.

The initial road surface gradient angle calculation unit 51, immediatelyafter the running-linked sound producing device 30 is powered on,calculates an initial gradient angle θ₀ of a road surface on which theelectric two-wheeled vehicle 1 is placed based on an output signal ofthe acceleration sensor 41. The running-linked sound producing device 30may be configured, for example, so as to be powered on simultaneouslywhen the electric two-wheeled vehicle 1 is powered on. The road surfacegradient angle calculation unit 52 determines a road surface gradientangle θ by integrating a pitch angular rate (angular rate about they-axis) detected by the angular rate sensor 42. More specifically, bytime integration of the pitch angular rate after the running-linkedsound producing device 30 is powered on with the initial gradient angleθ₀ used as an initial value, a road surface gradient angle θ isdetermined. That is, θ=θ₀+∫ (pitch angular rate) dt (t represents time).

The vehicle acceleration calculation unit 54 includes an accelerationestimating unit programmed to determine a fore-and-aft directionacceleration α of the electric two-wheeled vehicle 1 by applying acorrection based on the road surface gradient angle θ to a fore-and-aftdirection acceleration (x-axis direction acceleration) detected by theacceleration sensor 41. The vehicle speed calculation unit 55 determinesa vehicle speed V of the electric two-wheeled vehicle 1 by timeintegration of the fore-and-aft direction acceleration α. Morespecifically, the vehicle speed calculation unit 55 integrates thefore-and-aft direction acceleration α from power-on of therunning-linked sound producing device 30. An initial value ofintegration is made zero (cleared to zero with power-on). That is,V=∫αdt.

FIG. 4 is an explanatory view showing a state immediately after power-onon an inclined road surface 57. On the electric two-wheeled vehicle 1,gravity Mg (g is an acceleration of gravity) proportional to its mass Macts vertically downward. An x-axis direction component of the gravityMg can be expressed as Mg·sin θ₀ by using the initial road surfacegradient angle θ₀. Moreover, a z-axis direction component can beexpressed as Mg·cos θ₀ by using the initial road surface gradient angleθ₀. The acceleration sensor 41 detects a fore-and-aft directionacceleration, for example, with the front (+X direction, travelingdirection) of the electric two-wheeled vehicle 1 set as positive. Whenthe electric two-wheeled vehicle 1 is at a standstill on the roadsurface 57, an x-axis direction component Mg·sin θ₀ (force in a −Xdirection) of the gravity balances with a force Mα′ that acts toward thefront (+X direction) of the electric two-wheeled vehicle 1 in terms ofthe x-axis direction. Moreover, in terms of the z-axis direction, thez-axis direction component Mg·cos θ₀ of the gravity balances with anormal force Mβ′. In this regard, α′ represents an x-axis directionacceleration detected by the acceleration sensor 41, and β′ represents az-axis direction acceleration detected by the acceleration sensor 41.When the electric two-wheeled vehicle 1 is at a standstill, its actualacceleration α is zero, but an apparent acceleration α′ (=g sin θ₀) isdetected because of the x-axis direction component Mg·sin θ₀ of thegravity.

The acceleration sensor 41 detects the fore-and-aft directionacceleration α′ (=g sin θ₀) and an up-down direction (z-axis direction)acceleration β′ (=g cos θ₀) on the inclined road surface 57. Therefore,the initial gradient angle θ₀ can be determined as θ₀=Tan⁻¹ (α′/β′).This calculation is carried out in the initial road surface gradientangle calculation unit 51.

When the electric two-wheeled vehicle 1 is running on the road surface57 inclined at the road surface gradient angle θ, the fore-and-aftdirection acceleration α′ to be detected by the acceleration sensor 41takes a value for which a contribution component g sin θ of theacceleration of gravity g is added to a component of the actualfore-and-aft direction acceleration α of the electric two-wheeledvehicle 1. Accordingly, the vehicle acceleration calculation unit 54determines the actual fore-and-aft direction acceleration α (=α′−g sinθ) of the electric two-wheeled vehicle 1 by subtracting the contributioncomponent g sin θ of the acceleration of gravity g from the fore-and-aftdirection acceleration α′ detected by the acceleration sensor 41. Thatis, the vehicle acceleration calculation unit 54 determines afore-and-aft direction acceleration α of the electric two-wheeledvehicle 1 by applying a correction according to the road surfacegradient angle θ to an output signal of the acceleration sensor 41. Itsuffices to set the road surface gradient angle θ as positive when it isan elevation with respect to a horizontal plane, and as negative when itis a depression with respect to a horizontal plane, facing in thetraveling direction of the electric two-wheeled vehicle 1.

When the electric two-wheeled vehicle 1 is running, the accelerationsensor 41 easily detects a noise component due to road surfaceunevenness and vibration of the electric two-wheeled vehicle 1,especially, with regard to the z-axis direction. Further, with regard tothe x-axis direction, during running, both of an acceleration componentdue to a road surface inclination and an acceleration component due to achange in vehicle speed are contained in an output signal of theacceleration sensor 41, and it is difficult to distinguish between thosecomponents. Therefore, it is not practical to use an output signal ofthe acceleration sensor 41 to detect the gradient angle θ of a roadsurface on which the electric two-wheeled vehicle 1 is running.Accordingly, in the present preferred embodiment, the road surfacegradient angle θ is determined, after calculating the initial roadsurface gradient angle θ₀ based on an output signal of the accelerationsensor 41, by time integration of a pitch angular rate output by theangular rate sensor 42 with the initial road surface gradient angle θ₀used as an initial value of integration. Such an integration operationis carried out by the road surface gradient angle calculation unit 52.The road surface gradient angle θ thus determined is supplied to thevehicle acceleration calculation unit 54 for a correction of an outputsignal of the acceleration sensor 41.

The vehicle speed calculation unit 55 determines a vehicle speed V bytime integration of a fore-and-aft direction acceleration α obtained bya correction operation by the vehicle acceleration calculation unit 54.

FIG. 5 is a flowchart showing the content of processing by the vehiclespeed estimation unit 37.

The vehicle speed estimation unit 37 judges whether it is immediatelyafter power-on (step S1). When it is immediately after power-on, thevehicle speed estimation unit 37 reads in an output signal of theacceleration sensor 41 (step S2), and clears the vehicle speed V to zero(step S3). Further, the vehicle speed estimation unit 37 calculates aninitial road surface gradient angle θ₀ based on a fore-and-aft directionacceleration α′ and an up-down direction acceleration β′ taken in fromthe acceleration sensor 41 (step S4). The operation of steps S2 to S4 iscarried out only once immediately after power-on.

When it is not immediately after power-on (step S1: NO), the vehiclespeed estimation unit 37 reads in output signals of the accelerationsensor 41 and the angular rate sensor 42 (steps S5, S6). Then, thevehicle speed estimation unit 37 determines a gradient angle θ of a roadsurface on which the electric two-wheeled vehicle 1 is running byintegrating the output signal of the angular rate sensor 42 (step S7).Further, the vehicle speed estimation unit 37 determines an actualfore-and-aft direction acceleration α of the electric two-wheeledvehicle 1 by correcting the fore-and-aft direction acceleration α′(compensating for an acceleration of gravity component) output by theacceleration sensor 41 using the determined road surface gradient angleθ (step S8). Further, the vehicle speed estimation unit 37 determines acurrent vehicle speed V of the electric two-wheeled vehicle 1 by timeintegration of the fore-and-aft direction acceleration α (step S9).

Thereafter, the operation of steps S1 to S9 is repeated until the poweris shut off and the system stops.

FIG. 6 is a block diagram for explaining a configuration example of theaccelerator command value estimation unit 38. The accelerator commandvalue estimation unit 38 includes a torque estimation unit 60, a motorrotation speed computing unit 63, and an accelerator opening degreeestimation unit 65. The torque estimation unit 60 includes a runningresistance computing unit 61 and a necessary torque computing unit 62.The accelerator opening degree estimation unit 65 includes a producingtorque ratio calculation unit 66 and an estimated accelerator openingdegree calculation unit 67.

The motor rotation speed computing unit 63 includes a motor rotationspeed estimating unit and is programmed to compute a motor rotationspeed based on a vehicle speed V estimated by the vehicle speedestimation unit 37 and a predetermined conversion factor. The conversionfactor is a constant determined based on a reduction ratio and theperimeter of the rear wheel 4, and is provided from a storage unit(memory) built in the sound synthesizer circuit 35. By dividing thevehicle speed V by the perimeter of the rear wheel 4, the rotation speed(number of revolutions per unit time) of the rear wheel 4 is determined.Further, by multiplying the rotation speed of the rear wheel 4 by thereduction ratio, the rotation speed of the electric motor 5 isdetermined. The reduction ratio means a ratio between the rotation speedof the electric motor 5 and the rotation speed of the rear wheel 4(electric motor rotation speed/rear wheel rotation speed). Therefore, itsuffices to determine the conversion factor, for example, so as to beproportional to a product of a reciprocal of the perimeter of the rearwheel 4 and the reduction ratio. The computed motor rotation speed isprovided to the producing torque ratio calculation unit 66.

The running resistance computing unit 61 calculates an external force(running resistance) that hinders the electric two-wheeled vehicle 1traveling when the electric two-wheeled vehicle 1 is caused to run.Examples of running resistance components include an air resistance, aresistance due to tire deformation, and a resistance due to theviscosity of oil in the electric motor 5. The air resistance, which isproportional to the second power of the vehicle speed V, can thus beexpressed as Kar·V² by using a factor Kar. Other running resistancecomponents can be collectively expressed by a constant Lf. In thestorage unit (memory) included in the sound synthesizer circuit 35, thefactor Kar, the mass M of the electric two-wheeled vehicle 1, theacceleration of gravity g, and the constant Lf are written in advance.By using these constants and the vehicle speed V estimated by thevehicle speed estimation unit 37, the running resistance computing unit61 computes the running resistance=Kar·V²+Lf. The running resistancevalue is provided to the necessary torque computing unit 62.

The necessary torque computing unit 62 computes torque that needs to beproduced by the electric motor 5. When the electric two-wheeled vehicle1 is running at the acceleration α on a road surface with the roadsurface gradient angle θ, a force F to push the electric two-wheeledvehicle 1 in its traveling direction is given by F=runningresistance+Mg·sin θ+M·α. Mg·sin θ represents a resistance component dueto a road surface inclination, and is called a gradient resistance. M·αrepresents an acceleration resistance. Where a torque conversion factorof the electric motor 5 is K_(T) and necessary torque that needs to beproduced by the electric motor 5 is T₂, F=K_(T)·T₂ holds. Therefore, thenecessary torque T₂ is T₂=F/K_(T)=(running resistance+Mg·sinθ+M·α)/K_(T). This computation is carried out in the necessary torquecomputing unit 62. The computed necessary torque T₂ is provided to theproducing torque ratio calculation unit 66. The mass M, acceleration ofgravity g, and torque conversion factor K_(T) necessary for calculationof the necessary torque T₂ are provided from the storage unit (memory)included in the sound synthesizer circuit 35.

The producing torque ratio calculation unit 66 computes a producingtorque ratio based on the necessary toque T₂ and a motor rotation speed.The producing torque ratio means a ratio (T₂/T₁) of the necessary torqueT₂ to the maximum torque T₁ that can be produced by the electric motor 5at the motor rotation speed. The maximum torque T₁ is provided from amaximum torque map 64. An example of the maximum torque map 64 is shownin FIG. 7. That is, the maximum torque map 64 is defined by a data group(table) that stores a maximum torque map with respect to the motorrotation speed. The curve L1 shows actual torque characteristics of theelectric motor 5. The larger the motor rotation speed, the more themaximum torque T₁ decreases because of a back electromotive force. Theelectric motor 5 is capable of producing torque in a range not more thanthe maximum torque T₁ according to the motor rotation speed. Theproducing torque ratio calculation unit 66 reads out the maximum torqueT₁ corresponding to the motor rotation speed from the maximum torque map64, and computes a producing torque ratio T₂/T₁ using the read-outmaximum torque T₁.

Because the maximum torque map stored in the maximum torque map 64 isused only for production of a running-linked sound, it is not necessarythat the maximum torque map shows actual characteristics of the electricmotor 5. That is, as shown by the curves L2, L3, L4, and L5 in FIG. 7,it may be as well to compute the producing torque ratio T₂/T₁ using atorque characteristic curve different from that showing actualcharacteristics of the electric motor 5. For example, a plurality oftorque characteristic curves L1 to L5 may be stored in the maximumtorque map 64 so as to allow use while switching these curves by anoperation from a torque characteristic changing operation unit 71 (referto FIG. 6). As a result, characteristics of the sound synthesizercircuit 35 can be changed (tuned) according to characteristics of theelectric two-wheeled vehicle 1 and user preference. Further, changingcharacteristics of the maximum torque by an operation of the torquecharacteristic changing operation unit 71 makes it also possible to becompatible with a motor having any torque characteristics. Thus, thetorque characteristic changing operation unit 71 includes a motorcharacteristic changing unit programmed to change characteristics of themaximum torque with respect to the motor rotation speed.

The producing torque ratio T₂/T₁ thus determined is provided to theestimated accelerator opening degree calculation unit 67. The estimatedaccelerator opening degree calculation unit 67 determines an estimatedaccelerator opening degree as an accelerator command value withreference to an accelerator opening degree map 68. An example of theaccelerator opening degree map 68 is shown in FIG. 8. The acceleratoropening degree map 68 is defined by a data group (table) that stores anestimated accelerator opening degree (%) with respect to the producingtorque ratio. The accelerator opening degree means a ratio of an actualoperation amount of the accelerator grip with respect to the wholeoperation amount. The accelerator opening degree characteristic curveL11 shows characteristics simulating an actual relationship between theproducing torque ratio and accelerator opening degree. The larger theproducing torque ratio, the larger the estimated accelerator openingdegree. The estimated accelerator opening degree calculation unit 67reads out an estimated accelerator opening degree corresponding to theproduction ratio from the accelerator opening degree map 68, and outputsthe read-out estimated accelerator opening degree.

Because the accelerator opening degree map stored in the acceleratoropening degree map 68 is used only for production of a running-linkedsound, it is not necessary that the accelerator opening degree mapalways simulates actual accelerator opening degree characteristics. Thatis, as shown by the curves L12, L13, L14, and L15, it may be as well todetermine the estimated accelerator opening degree using an acceleratoropening degree characteristic curve different from that showing actualaccelerator opening degree characteristics. For example, a plurality ofaccelerator opening degree characteristic curves L11 to L15 may bestored in the accelerator opening degree map 68 so as to allow use whileswitching these curves by an operation from an accelerator openingdegree characteristic changing operation unit 72 (refer to FIG. 6). As aresult, characteristics of the sound synthesizer circuit 35 can bechanged (tuned) according to characteristics of the electric two-wheeledvehicle 1 and user preference. Thus, the accelerator opening degreecharacteristic changing operation unit 72 includes an acceleratorcharacteristic changing unit programmed to change characteristics of theaccelerator command value with respect to the producing torque ratio.

FIG. 9 is a flowchart collectively showing a processing by theaccelerator command value estimation unit 38. The accelerator commandvalue estimation unit 38 reads in a vehicle speed V estimated by thevehicle speed estimation unit 37 and a road surface gradient angle θestimated by the road surface gradient estimation unit 50 (steps S11,S12). Further, the accelerator command value estimation unit 38, basedon the vehicle speed V and the road surface gradient angle θ, calculatesa running resistance (step S13). Further, the accelerator command valueestimation unit 38 reads in a fore-and-aft direction acceleration α towhich a correction regarding a road surface gradient has been applied bythe vehicle acceleration calculation unit 54 (step S14). Then, theaccelerator command value estimation unit 38 determines a necessarytorque T₂ based on the fore-and-aft direction acceleration α, therunning resistance, and the road surface gradient angle θ (step S15). Onthe other hand, the accelerator command value estimation unit 38determines a motor rotation speed based on the vehicle speed V (stepS16). Then, the accelerator command value estimation unit 38 reads outthe maximum torque T₁ from the maximum torque map 64 based on thedetermined motor rotation speed (step S17), and calculates a producingtorque ratio T₂/T₁ using the same (step S18). Further, the acceleratorcommand value estimation unit 38 determines an estimated acceleratoropening degree as an estimated accelerator command value by makingreference to the accelerator opening degree map 68 using the producingtorque ratio T₂/T₁ (step S19). This operation is repeated until thesystem stops due to power-off.

FIG. 10 is a block diagram showing a configuration example of therunning-linked sound generation unit 39. The running-linked soundgeneration unit 39 uses a vehicle speed V estimated by the vehicle speedestimation unit 37, a vehicle acceleration α calculated by the vehicleacceleration calculation unit 54, and an estimated accelerator openingdegree determined by the accelerator command value estimation unit 38.The running-linked sound generation unit 39 using the above produces arunning-linked sound signal according to a running state of the electrictwo-wheeled vehicle 1.

In the present preferred embodiment, a virtual engine (internalcombustion engine) whose operating state changes according to therunning state of the electric two-wheeled vehicle 1 is assumed, and anengine sound that needs to be produced by the virtual engine accordingto its operating state is synthesized as a running-linked sound.Further, in the present preferred embodiment, an engine sound is dividedand handled as a plurality of components. Specifically, engine sounddata is divided and handled as an order sound component being a firstcomponent and a random sound component being a second component. Theorder sound component means a sound component, of an engine sound (or asound produced by a vehicle powered by an engine), whose frequency (orfrequency spectrum) fluctuates according to the engine speed. The randomsound component means a component, of an engine sound (or a soundproduced by a vehicle powered by an engine), whose frequency (orfrequency spectrum) does not substantially fluctuate regardless of theengine speed.

The running-linked sound generation unit 39 includes a virtual enginespeed calculation unit 80 as an example of a motor rotation speedestimating unit, an order sound data generation unit 91, a random sounddata generation unit 92, and a synthesis unit 90.

The virtual engine speed calculation unit 80 calculates a rotation speedof the virtual engine based on a vehicle speed V estimated by thevehicle speed estimation unit 37, an estimated accelerator openingdegree estimated by the accelerator command value estimation unit 38,and a vehicle acceleration α calculated by the vehicle accelerationcalculation unit 54. More specifically, the virtual engine speedcalculation unit 80 makes reference to the virtual engine speed map 79based on the vehicle speed V, the estimated accelerator opening degree,and the vehicle acceleration α, and reads out a corresponding virtualengine speed from the virtual engine speed map 79. The read-out virtualengine speed is provided to the order sound data generation unit 91.

The order sound data generation unit 91 includes a first component sounddata generating unit programmed to generate order sound data, of anengine sound, representing an order sound component as a firstcomponent. The order sound data generation unit 91 includes a basicorder sound data storage unit 81, an order sound reproduction timecalculation unit 82, an order sound data reproduction unit 83, an ordersound gain generation unit 84, and an order sound gain multiplicationunit 85. The basic order sound data storage unit 81 stores, as firstcomponent basic sound data, basic order sound data prepared in advance.The basic order sound data is data representing only an order soundcomponent of an engine sound generated when the virtual engine isrotating at a basic rotation speed (for example, 3000 rpm), and has acertain length of time (basic reproduction time). The basic order sounddata may be prepared by processing sound data recorded from an actualengine, or may be sound data prepared by a computer to resemble actualorder sound data without using data recorded from an actual engine.However, it is preferable that the basic order sound data contains assmall a random sound component as possible. That is, it is preferablethat the basic order sound data does not contain a random soundcomponent at all or is sound data with a random sound component reduced.

The order sound reproduction time calculation unit 82 calculates areproduction time of basic order sound data based on a virtual enginespeed. The reproduction time is calculated by the following formula.Reproduction time=Basic reproduction time×Basic rotation speed/Virtualengine speed.

That is, the reproduction time of basic order sound data is determinedby modifying the basic reproduction time so as to be inverselyproportional to the virtual engine speed. Therefore, the reproductiontime is short at high-speed rotation (that is, at high-speed running),and the reproduction time is long at low-speed rotation (that is, atlow-speed running).

The order sound data reproduction unit 83 reads out basic order sounddata from the basic order sound data storage unit 81, and repeatedlyreproduces (loop-reproduces) the basic order sound data with areproduction time calculated by the order sound reproduction timecalculation unit 82. The shorter the production time, the higher thetone of a sound to be reproduced, and the longer the reproduction time,the lower the tone of a sound to be reproduced. Therefore, an ordersound with a high tone can be generated at high-speed rotation, and anorder sound with a low tone can be generated at low-speed rotation. Thatis, the order sound reproduction time calculation unit 82 and the ordersound data reproduction unit 83 constitute a tone changing unitprogrammed to change the tone of an order sound component according to avirtual engine speed. The basic order sound data repeatedly reproducedby the order sound data reproduction unit 83 is provided to the ordersound gain multiplication unit 85.

The order sound gain multiplication unit 85 generates volume-adjustedorder sound data by multiplying repeatedly reproduced basic order sounddata by an order sound gain generated by the order sound gain generationunit 84. The order sound data is provided to the synthesis unit 90. Theorder sound gain generation unit 84 generates an order sound gainaccording to an accelerator opening degree and a virtual engine speed.Therefore, the volume of an order sound component changes according tothe accelerator opening degree and virtual engine speed. That is, theorder sound gain generation unit 84 and the order sound gainmultiplication unit 85 constitute an order sound component volumechanging unit programmed to change the volume of an order soundcomponent according to a virtual engine speed and an accelerator openingdegree.

The random sound data generation unit 92 includes a second componentsound data generating unit programmed to generate random sound data, ofan engine sound, representing a random sound component as a secondcomponent. The random sound data generation unit 92 includes a basicrandom sound data storage unit 86, a random sound data reproduction unit87, a random sound gain generation unit 88, and a random sound gainmultiplication unit 89. The basic random sound data storage unit 86stores, as second component basic sound data, basic random sound dataprepared in advance. The basic random sound data is data representingonly a random sound component of an engine sound generated when thevirtual engine is rotating at a basic rotation speed (for example, 3000rpm), and has a certain length of time (basic reproduction time). Thebasic random sound data may be prepared by processing sound datarecorded from an actual engine, or may be sound data prepared by acomputer to resemble actual random sound data without using datarecorded from an actual engine. However, it is preferable that the basicrandom sound data contains as small an order sound component aspossible. That is, it is preferable that the basic random sound datadoes not contain an order sound component at all or is sound data withan order sound component reduced.

The random sound data reproduction unit 87 reads out basic random sounddata from the basic random sound data storage unit 86, and repeatedlyreproduces the basic random sound data with a basic reproduction time.Because the basic random sound data is always reproduced with the basicreproduction time, its tone does not change. The basic random sound datarepeatedly reproduced by the random sound data reproduction unit 87 isprovided to the random sound gain multiplication unit 89. The randomsound gain multiplication unit 89 generates volume-adjusted random sounddata by multiplying repeatedly reproduced basic random sound data by arandom sound gain generated by the random sound gain generation unit 88.The random sound data is provided to the synthesis unit 90. The randomsound gain generation unit 88 generates a random sound gain according toan accelerator opening degree and a virtual engine speed. Therefore, thevolume of a random sound component changes according to the acceleratoropening degree and virtual engine speed. That is, the random sound gaingeneration unit 88 and the random sound gain multiplication unit 89constitute a random sound component volume changing unit programmed tochange the volume of a random sound component according to a virtualengine speed and an accelerator opening degree.

The synthesis unit 90 includes a synthetic sound data generating unitprogrammed to synthesize, by superimposing, order sound data generatedby the order sound data generation unit 91 and random sound datagenerated by the random sound data generation unit 92, and to generatesynthetic engine sound data (running-linked sound signal). The syntheticengine sound data is provided to the amplifier 36 and amplified. Theamplifier 36 converts the synthetic engine sound data to an analogsignal, and amplifies the analog signal to generate an audio signal todrive the speaker 32.

FIG. 11A shows an example of the virtual engine speed map 79. In thisexample, the virtual engine speed map includes a first section 101 inwhich the virtual engine speed is constant at an idling engine speedfrom a vehicle speed of zero to a first vehicle speed threshold V1, anda linear second section 102 that is continuous from the first section101 at the first vehicle speed threshold V1 and extending along a basicline 100 proportional to the vehicle speed. Further, the virtual enginespeed map includes a linear third section 103 in which the virtualengine speed increases with the vehicle speed at a constant change ratefrom the idling engine speed in a section from a vehicle speed of zeroto a second vehicle speed threshold V2. The virtual engine speed mapfurther includes a fourth section 104 that is continuous from the thirdsection 103 at the second vehicle speed threshold V2, keeping a constantvirtual engine speed N1 regardless of the vehicle speed, and continuousto the second section 102 at a third vehicle speed threshold V3.

When the vehicle acceleration α is negative, that is, at the time ofdeceleration, a virtual engine speed along the first section 101 and thesecond section 102 is read out based on a current vehicle speed V. Onthe other hand, when the vehicle acceleration α is positive, that is, atthe time of acceleration, and with a vehicle speed of the third vehiclethreshold V3 or more, a virtual engine speed along the second section102 is read out based on a current vehicle speed. In contrast thereto,when the vehicle is accelerating at a vehicle speed V less than thethird vehicle speed threshold V3, a virtual engine speed is determinedin accordance with a constant engine speed line NV that is obtained byprorating a section between the first section 101 and the fourth section104 according to an accelerator opening degree with regard to the enginespeed coordinate axis direction.

FIG. 11B shows a constant engine speed line NV when the electrictwo-wheeled vehicle 1 is accelerating in a state with a relatively smallvalue of the accelerator opening degree. The constant engine speed lineNV in this case is set at a position close to the first section 101, andis defined by a segment showing a constant virtual engine speedregardless of the vehicle speed V. The constant engine speed line NV iscontinuous at its low-speed side end from the third section 103, and iscontinuous at its high-speed side end to the second section 102.Therefore, when the electric two-wheeled vehicle 1 accelerates from astopped state, the virtual engine speed is first determined inaccordance with the third section 103, and then the virtual engine speedis determined in accordance with the constant engine speed line NV. Whenthe vehicle is further accelerated, the virtual engine speed isdetermined in accordance with the second section 102. The constantengine speed line NV when the accelerator opening degree is 0% iscoincident with the first section 101.

FIG. 11C shows a constant engine speed line NV when the electrictwo-wheeled vehicle 1 is accelerating in a state with a relatively largeaccelerator opening degree. The constant engine speed line NV in thiscase is set at a position close to the fourth section 104, and isdefined by a segment showing a constant virtual engine speed regardlessof the vehicle speed V. The constant engine speed line NV is continuousat its low-speed side end from the third section 103, and is continuousat its high-speed side end to the second section 102. The constantengine speed line NV when the accelerator opening degree is 100% iscoincident with the fourth section 104.

When the vehicle acceleration α is zero, that is, during constant-speedrunning, a virtual engine speed is determined in accordance with acharacteristic line that is referred to at that point in time fordetermination of a virtual engine speed.

FIG. 11D and FIG. 11E show operations when the vehicle acceleration αhas changed from a positive value to a negative value in determinationof a virtual engine speed in accordance with a constant engine speedline NV. In this case, at a point in time where the vehicle accelerationα has changed to a negative value, the characteristic line that needs tobe referred to is switched from the constant engine speed line NV to thefirst section 101 or the second section 102 according to a vehicle speedV at that time.

FIG. 11F shows behavior when the vehicle acceleration α has once changedto a negative value from a state of determining a virtual engine speedin accordance with the third section 103, and then the vehicleacceleration α has changed to a positive value. That is, it correspondsto a case where the electric two-wheeled vehicle 1 in acceleration oncechanges to deceleration, and then again changes to acceleration as aresult of the accelerator opening degree being maximized (100%). In thiscase, the characteristic line that needs to be referred to is onceswitched to the first section 101 from a state of determining a virtualengine speed with reference to the third section 103, and then the thirdsection 103 again serves as a referring characteristic line.

FIG. 12 is a view for explaining a configuration example of the ordersound gain generation unit 84. The order sound gain generation unit 84includes a first order sound gain setting unit 94, a second order soundgain setting unit 95, and a multiplication unit 96. The first ordersound gain setting unit 94 sets a first order sound gain K_(d1)according to the accelerator opening degree. The second order sound gainsetting unit 95 sets a second order sound gain K_(d2) according to thevirtual engine speed. The multiplication unit 96 determines an ordersound gain K_(d) (=K_(d2)×K_(d2)) by multiplying the first order soundgain K_(d1) and the second order sound gain K_(d2) by each other. Theorder sound gain K_(d) is provided to the order sound gainmultiplication unit 85 (refer to FIG. 10).

The first order sound gain K_(d1) is set, for example, in accordancewith a characteristic curve (map data) that monotonously increases fromthe minimum value larger than 0 to the maximum value “1” when theestimated accelerator opening degree increases from 0% to 100%. In theexample of FIG. 12, the first order sound gain K_(d1) is set so as tononlinearly and monotonously increase with an increase in the estimatedaccelerator opening degree, and its rate of increase is smaller as theestimated accelerator opening degree is larger.

The second order sound gain K_(d2) is set, for example, in accordancewith a characteristic curve (map data) that monotonously increases fromthe minimum value “0” to the maximum value “1” when the virtual enginespeed increases from 0 to the maximum value MAX. In the example of FIG.12, the second order sound gain K_(d2) monotonously increases so as tobe substantially proportional to the virtual engine speed, and saturatesto the maximum value “1” in a region of a virtual engine speed or moresmaller than the maximum engine speed MAX.

The characteristic curves to provide the first and second order soundgains K_(d1), K_(d2) are mere examples, and other characteristic curvescan of course be used. Alternatively, one or both of the characteristiccurves to provide the first and second order sound gains K_(d1), K_(d2)may be prepared in a plurality of types so as to allow selecting thosecurves according to the type of the electric two-wheeled vehicle 1 anduser preference. As a result, the volume characteristics of an ordersound with respect to the estimated accelerator opening degree and/orvirtual engine speed can be tuned.

FIG. 13 is a view for explaining a configuration example of the randomsound gain generation unit 88. The random sound gain generation unit 88includes a first random sound gain setting unit 97, a second randomsound gain setting unit 98, and a multiplication unit 99. The firstrandom sound gain setting unit 97 sets a first random sound gain K_(r1)according to the accelerator opening degree. The second random soundgain setting unit 98 sets a second random sound gain K_(r2) according tothe virtual engine speed. The multiplication unit 99 determines a randomsound gain K_(r) (=K_(r1)×K_(r2)) by multiplying the first random soundgain K_(r1) and the second random sound gain K_(r2) by each other. Therandom sound gain K_(r) is provided to the random sound gainmultiplication unit 89 (refer to FIG. 10).

The first random sound gain K_(r1) is set, for example, in accordancewith a characteristic curve (map data) that monotonously increases fromthe minimum value larger than 0 to the maximum value “1” when theestimated accelerator opening degree increases from 0% to 100%. In theexample of FIG. 13, the first random sound gain K_(r1) is set so as tononlinearly and monotonously increase with an increase in the estimatedaccelerator opening degree, and its rate of increase is smaller as theestimated accelerator opening degree is larger.

The second random sound gain K_(r2) is set, for example, in accordancewith a characteristic curve (map data) that monotonously increases fromthe minimum value “0” to the maximum value “1” when the virtual enginespeed increases from 0 to the maximum value MAX. In the example of FIG.13, the second random sound gain K_(r2) nonlinearly and monotonouslyincreases with an increase in the virtual engine speed, and its rate ofincrease is smaller as the virtual engine speed is larger. In addition,the second random sound gain K_(r2) saturates to the maximum value “1”in a region of a virtual engine speed or more smaller than the maximumengine speed MAX.

The characteristic curves to provide the first and second random soundgains K_(r1), K_(r2) are mere examples, and other characteristic curvescan of course be used. Alternatively, one or both of the characteristiccurves to provide the first and second random sound gains K_(r1), K_(r2)may be prepared in a plurality of types so as to allow selecting thosecurves according to the type of the electric two-wheeled vehicle 1 anduser preference. As a result, the volume characteristics of a randomsound with respect to the estimated accelerator opening degree and/orvirtual engine speed can be tuned.

FIG. 14A is a view for explaining changes in order sound data accordingto the accelerator opening degree and virtual engine speed. The volumeof the order sound data is changed to be higher as the virtual enginespeed is larger and to be higher as the accelerator opening degree islarger. Moreover, the tone of the order sound data is changed to behigher as the virtual engine speed is larger, and does not depend on theaccelerator opening degree.

FIG. 14B is a view for explaining changes in random sound data accordingto the accelerator opening degree and virtual engine speed. The volumeof the random sound data is changed to be higher as the virtual enginespeed is larger and to be higher as the accelerator opening degree islarger. Moreover, the tone of the random sound data does not depend onthe virtual engine speed or the accelerator opening degree.

FIG. 15 shows an example where order sound data was reproduced andfrequency-analyzed. The horizontal axis shows time, and the verticalaxis shows frequency. Shown are reproduction results of order sound datawhen the accelerator opening degree was increased quickly from 0% to100% at a timing to start acceleration and then kept at 100%, and thenwas quickly reduced to 0% after the engine speed rose to a predeterminedvalue. The virtual engine speed has increased and decreased according toan increase and decrease in the accelerator opening degree, and theorder sound frequency increases and decreases accordingly. The intensityof frequency components in a harmonic (overtone) relationship appearsstrongly.

When the same reproduction is performed for random sound data, there isa distribution of wide-band noise components having such frequencycharacteristics that low-frequency components are large and the soundpressure is reduced toward higher frequencies in a coordinate plane withrectangular coordinates of time and frequency, and the sound pressure asa whole increases and decreases with a rise/fall in engine speed. Thatis, the spectral shape does not depend on time, and it is understoodthat a random sound does not depend on the virtual engine speed.

As in the above, according to the present preferred embodiment, avehicle speed is estimated based on output signals of the accelerationsensor 41 and the angular rate sensor 42 provided in the running-linkedsound producing device 30 (built in, for example, a case of the devicemain body 31). Therefore, because it is not necessary to obtain vehiclespeed information from the vehicle body of the electric two-wheeledvehicle 1, a wiring therefor is not required. Moreover, because anaccelerator command value (accelerator opening degree) is also estimatedbased on the estimated vehicle speed, a wiring for obtaining theoperation amount of the accelerator grip from the vehicle body of theelectric two-wheeled vehicle 1 is also not required. Therefore, becausewirings can be reduced, the configuration of the running-linked soundproducing device 30 can be simplified, and fitting to the electrictwo-wheeled vehicle 1 also becomes easy. Nevertheless, a running-linkedsound according to the estimated vehicle speed and accelerator commandvalue is generated, so that an appropriate running-linked soundaccording to the running state of the electric two-wheeled vehicle 1 canbe produced.

The prior art of Japanese Unexamined Patent Application Publication No.2000-1142 may be suitable for four-wheeled vehicles, but there are stillmany challenges to be solved in applying the prior art to vehicles ofmore simple structures represented by two-wheeled vehicles including theelectric two-wheeled vehicle 1. For example, in a four-wheeled vehicle,output signals of sensors are easily obtained because an in-vehicle LANis equipped. On the other hand, in a vehicle without an in-vehicle LANand with a simple arrangement of electrical components, such as atwo-wheeled vehicle, it is not easy to obtain sensor signals. Even whensensor signals can be obtained by adding wirings, a large number ofwirings are required, so that not only is the structure complicated, butthe number of fitting steps is also increased, and it is inevitable thatthe cost is increased accordingly. For two-wheeled vehicles and the likethat are lower priced than four-wheeled vehicles, low-cost equipment isdemanded accordingly, so that widespread use of a costly device isdifficult.

The present preferred embodiment solves such technical challenges, andprovides a running-linked sound producing device which has a simpleconfiguration and is also easily fitted to a vehicle. The running-linkedsound producing device of the present preferred embodiment does notrequire a large number of wiring connections when being fitted aftercompletion of a vehicle body, let alone when being mounted duringassembly of a vehicle body, and can therefore be easily mounted on thevehicle body. Of course, wiring connections for input of sensor signalsare also not necessary when the device is replaced, making the workeasy.

Further, in the present preferred embodiment, because the torqueestimation unit 60 that estimates the producing torque (necessary torqueT₂) of the electric motor 5 according to an estimated vehicle speed isprovided, it is not necessary to obtain information for estimating theproducing torque from the vehicle. Then, because an accelerator openingdegree as an accelerator command value is estimated according to theestimated producing torque, the accelerator opening degree can beaccurately estimated. That is, an output (producing torque) of theelectric motor 5 is estimated from the vehicle speed, and an acceleratoropening degree to produce the output is estimated.

Further, in the present preferred embodiment, the torque estimation unit60 includes a running resistance computing unit 61 and a necessarytorque computing unit 62. The accelerator opening degree estimation unit65 estimates an accelerator opening degree based on the necessary torqueT₂ computed by the necessary torque computing unit 62 and the motorrotation speed estimated from the vehicle speed V. As a result, theaccelerator opening degree can be more accurately estimated, so that arunning-linked sound matching the running state of the electrictwo-wheeled vehicle 1 can be produced.

Furthermore, in the present preferred embodiment, the necessary torquecomputing unit 62 is programmed to compute necessary torque T₂ based onthe running resistance, the vehicle acceleration α estimated by thevehicle acceleration calculation unit 54, and the road surface gradientangle θ estimated by the road surface gradient estimation unit 50.Therefore, the necessary torque T₂ is computed based on not only therunning resistance but also the estimated acceleration and road surfacegradient. By using such necessary torque T₂, the accelerator openingdegree can be accurately estimated, so that a running-linked soundreflecting the running state of the electric two-wheeled vehicle 1 canbe produced more accurately.

Further, in the present preferred embodiment, the accelerator openingdegree estimation unit 65 includes a producing torque ratio calculationunit 66 that computes a producing torque ratio (T₂/T₁) being a ratio ofthe necessary torque T₂ to the maximum torque T₁ that can be produced bythe electric motor 5. An accelerator opening degree is estimated basedon the producing torque ratio (T₂/T₁). As a result, the acceleratoropening degree can be more appropriately estimated, so that arunning-linked sound reflecting the running state of the electrictwo-wheeled vehicle 1 can be produced more accurately.

Moreover, in the present preferred embodiment, the output (accelerationα′) of the acceleration sensor 41 is corrected according to the roadsurface gradient angle θ estimated by the road surface gradientestimation unit 50, and the corrected acceleration α is integrated toestimate a vehicle speed V. This arrangement, when the acceleration ofgravity g has an influence on the output of the acceleration sensor 41due to a road surface gradient, allows determining a vehicleacceleration α of the electric two-wheeled vehicle 1 reducing oreliminating the influence. As a result, estimation of a vehicle speed Vbased on the vehicle acceleration α can be accurately performed, so thata running-linked sound matching the running state of the electrictwo-wheeled vehicle 1 can be produced.

Moreover, in the present preferred embodiment, an angular rate detectedby the angular speed sensor 42 built in the device main body 31 isintegrated to estimate a gradient angle θ of a road surface on which theelectric two-wheeled vehicle 1 is running. Therefore, the road surfacegradient angle θ can be determined without providing a sensor fordirectly detecting a road surface gradient. As a result, a running stateof the electric two-wheeled vehicle 1 reflecting a road surface gradientcan be determined with a simple configuration, and accordingly, arunning-linked sound matching the running state of the electrictwo-wheeled vehicle 1 can be produced.

Moreover, in the present preferred embodiment, a motor rotation speed isdetermined, based on the estimated vehicle speed V, by the motorrotation speed computing unit 63. Therefore, it is not necessary toobtain information concerning the motor rotation speed from the vehiclebody of the electric two-wheeled vehicle 1. Therefore, therunning-linked sound producing device 30 can be equipped on the electrictwo-wheeled vehicle 1 at a low cost, and can produce a running-linkedsound that is appropriately linked to the running state of the electrictwo-wheeled vehicle 1.

Moreover, in the present preferred embodiment, a virtual engine speed isdetermined, based on the estimated vehicle speed V and estimatedaccelerator opening degree, by the virtual engine speed calculation unit80. As a result, a virtual engine speed can be obtained withoutobtaining information concerning the engine speed from the vehicle bodyof the electric two-wheeled vehicle 1. However, in the present preferredembodiment, the electric two-wheeled vehicle 1 cannot generate enginespeed information because it is not provided with an engine. In eithercase, because it is not necessary to obtain engine speed informationfrom the vehicle body, the running-linked sound producing device 30 canbe equipped on the electric two-wheeled vehicle 1 at a low cost, and canproduce an internally generated running-linked sound according to thevirtual engine speed.

Moreover, according to the present preferred embodiment, the order sounddata generation unit 91 changes the tone of basic order sound dataaccording to the virtual engine speed, and further changes the volumethereof according to the virtual engine speed and accelerator openingdegree to generate order sound data. Moreover, the random sound datageneration unit 92 does not change the tone of basic random sound data,and changes the volume thereof according to the virtual engine speed andaccelerator opening degree to generate random sound data. As a result ofthese sound data being superimposed with each other in the synthesisunit 90, synthetic engine sound data is generated.

As a result, a natural engine sound close to an actual engine sound canbe generated as a running-linked sound. That is, a deep (with a sense ofdepth), comfortable engine sound can be synthesized. Furthermore,because synthetic engine sound data is obtained by generating ordersound data by changing the tone and volume of basic order sound data,generating random sound data by changing the volume of basic randomsound data, and combining these sound data, the configuration is simple.Therefore, a comfortable natural engine sound can be generated as arunning-linked sound with the simple configuration.

An engine sound produced by an engine as an example of a motor includesan order sound component whose frequency changes proportional to theengine speed and a random sound component whose frequency does notchange depending on the engine speed. For example, the frequency of anorder sound is proportional to the explosion frequency of an engine. Forexample, when a 2-stroke 1-cylinder engine is operated at an enginespeed of 6000 rpm (100 revolutions per second), a sound of a fundamentalwave of 100 Hz and its harmonics is produced. If the engine speed is ahalf, 3000 rpm, a sound of a fundamental wave of 50 Hz and its harmonicsis produced. These are order sound components. The higher the enginespeed and the larger the engine load (accelerator opening degree), thelarger the volume of an order sound component. The frequency of a randomsound component has nothing to do with the engine speed, and the higherthe engine speed and the larger the engine load (accelerator openingdegree), the larger the volume thereof.

The same applies to a motor sound produced by an electric motor beinganother example of a motor. That is, a motor sound includes an ordersound component whose frequency fluctuates depending on the motorrotation speed and a random sound component whose frequency tendencydoes not change even when the motor rotation speed changes. For both theorder sound component and random sound component, the volume is higheras the motor rotation speed is larger and larger as the motor load(motor current) is larger.

In the conventional technology of simulated sound synthesis forsynthesizing a simulated sound of a motor, as described also in JapaneseUnexamined Patent Application Publication No. 2000-1142, an actual motorsound is recorded to prepare basic sound data, and the volume andreproduction time of the basic sound data is changed to synthesize asimulated sound. The present inventor has focused on the fact that asimulated sound thus synthesized results in an unnatural sound differentfrom the sound produced by an actual motor, and discovered that thecause is that basic sound data contains not only an order soundcomponent but also a random sound component. That is, when thereproduction time of basic sound data is changed, the tones of both anorder sound component and a random sound component contained in thebasic sound data change equally, so that a simulated sound that gives anunnatural impression is generated. Accordingly, the present inventor hasprepared basic order sound data and basic random sound data separatelyby a computer. Then, as a result of changing the tone of the basic ordersound data according to the motor rotation speed while not changing thetone of the basic random sound data and combining these data, thepresent inventor has discovered that a natural simulated sound to givean impression close to that of the sound produced by an actual motor isobtained. That is, the foregoing preferred embodiment is based on thediscovery of a new challenge in simulated sound synthesis, and providesa solution for that challenge.

FIG. 16A and FIG. 16B explain a running-linked sound producing deviceaccording to another preferred embodiment of the present invention,showing another configuration example for vehicle speed estimation. Morespecifically, in the present preferred embodiment, as shown by thealternate long and two short dashed line in FIG. 2, the running-linkedsound producing device 30 includes a GPS receiver 45, which is providedin the case of the device main body 31. The vehicle speed estimationunit 37 is programmed to estimate a vehicle speed of the electrictwo-wheeled vehicle 1 using an output signal of the GPS receiver 45. TheGPS receiver 45 receives radio waves from three GPS satellites 46-1,46-2, 46-3 out of a plurality of GPS satellites orbiting the earth tocarry out positioning, and outputs position data representing itscurrent position.

The GPS receiver 45 receives signals from the GPS satellites 46-1, 46-2,46-3 at a first spot A (step S21), and generates first position datarepresenting the position of the first spot A based on the receivedsignals (step S22). The first position data includes positioninformation of the first spot A and information on time (positioningtime) for which the GPS receiver 45 has received radio waves at thefirst spot A. The vehicle speed estimation unit 37 obtains the firstposition data (step S23).

Further, after an elapse of a certain time, the GPS receiver 45 receivessignals from the GPS satellites 46-1, 46-2, 46-3 at a second spot B(step S24), and generates second position data representing the positionof the second spot B based on the received signals (step S25). Thesecond position data includes position information of the second spot Band information on time (positioning time) for which the GPS receiver 45has received radio waves at the second spot B. The vehicle speedestimation unit 37 obtains the second position data (step S26).

The vehicle speed estimation unit 37, based on the first position dataand second position data, calculates a distance (moving distance)between the first spot A and the second spot B (step S27), and furthercalculates time (moving time) required for a movement between thosespots (step S28). The vehicle speed estimation unit 37 calculates avehicle speed V (=moving distance/moving time) by dividing the movingdistance by the moving time (step S29). This operation is repeated untilsystem termination, that is, power-off of the running-linked soundproducing device 30 (step S30).

Also with such a configuration, the running-linked sound producingdevice 30 can estimate a vehicle speed of the electric two-wheeledvehicle 1 without obtaining a signal for vehicle speed estimation fromthe vehicle body of the electric two-wheeled vehicle 1. As a result, arunning-linked sound producing device 30 which has a simpleconfiguration, is easily fitted to the electric two-wheeled vehicle 1,and can produce a running-linked sound corresponding to the runningstate of the electric two-wheeled vehicle 1 can be provided.

FIG. 17 explains a running-linked sound producing device according tostill another preferred embodiment of the present invention, showinganother configuration example for vehicle speed estimation. Similarly tothe preferred embodiment described with reference to FIG. 16A and FIG.16B, the present preferred embodiment also uses an output of the GPSreceiver 45. However, in the present preferred embodiment, the GPSreceiver 45 outputs not only position data but also moving speed data.More specifically, the GPS receiver 45 has a speed calculating functionto calculate a moving speed of the GPS receiver 45 by using the Dopplereffect of carrier waves from the GPS satellites 46-1, 46-2, 46-3 (referto FIG. 16A).

More specifically, a first vehicle speed V1 is estimated, using positiondata generated by the GPS receiver 45, through the same steps S21 to S29as with the case of FIG. 16B. Further, the vehicle speed estimation unit37 obtains as a second vehicle speed V2 moving speed data generated bythe GPS receiver 45 at the second spot B (step S31). Further, thevehicle speed estimation unit 37 judges whether a difference |V1-V2|between the first vehicle speed V1 and the second vehicle speed V2 isless than a predetermined allowable value (constant value) (step S32).If the difference is less than the allowable value (or not more than theallowable value), the second vehicle speed V2 is set as a currentvehicle speed V (step S33). If the difference is not less than theallowable value (or exceeds the allowable value), the first vehiclespeed V1 is set as a current vehicle speed V (step S34). This operationis repeated until the system termination, that is, power-off of therunning-linked sound producing device 30 (step S30).

The first vehicle speed V1 is calculated at a point in time where thevehicle has moved from the first spot A to the second spot B, and isthus accurate, but it takes time until a vehicle speed can be estimated.That is, updating takes time. The second vehicle speed V2 can bepromptly obtained from the GPS receiver 45, but sometimes contains alarge error depending on the reception status of radio waves from theGPS satellites. Therefore, in the present preferred embodiment, when thedifference between the first and second vehicle speeds V1, V2 is lessthan the allowable value, the second vehicle speed V2 is used as thevehicle value V considering that the value of the second vehicle speedV2 measured by using the Doppler effect is reliable. When the differencebetween the first and second vehicle speeds V1, V2 is not less than theallowable value, the second vehicle speed V2 is considered to beunreliable, and the first vehicle speed V1 is used.

Thus, also with the present preferred embodiment, a vehicle speed can beestimated without obtaining information from the vehicle body of theelectric two-wheeled vehicle 1. Therefore, a running-linked soundproducing device 30 which has a simple configuration and is easilyfitted to the electric two-wheeled vehicle 1, but can produce arunning-linked sound corresponding to the running state can be provided.

Although, in the preferred embodiment of FIG. 17, position data andspeed data generated by the GPS receiver 45 are preferably used, asecond GPS receiver for generating speed data may be provided besides afirst GPS receiver for generating position data. In this case, itsuffices to obtain position data from the first GPS receiver and obtainspeed data from the second GPS receiver. The speed data generated by theGPS receiver is used not for running control of the electric two-wheeledvehicle 1, but is merely used for generation of a running-linked sound.Therefore, it does not matter even when the speed data contains someerrors. Therefore, a vehicle speed of the electric two-wheeled vehicle 1may be estimated exclusively using the speed data generated by the GPSreceiver.

Although the preferred embodiments of the present invention have beendescribed as above, the present invention can also be carried out bystill other preferred embodiments. For example, in the foregoingpreferred embodiments, the electric two-wheeled vehicle 1 has beenmentioned as an example of a vehicle, but a preferred embodiment of thepresent invention can be applied also to a vehicle having an engine(internal combustion engine) as its power source. Of course, a preferredembodiment of the present invention may be applied to a hybrid typevehicle having as its power sources both an electric motor and engine.Of course, a preferred embodiment of the present invention can beapplied also to a vehicle other than a two-wheeled vehicle.

Moreover, in the foregoing preferred embodiments, description has beengiven of a running-linked sound producing device that generates anengine sound (simulated engine sound) as a running-linked sound, but therunning-linked sound may be other than an engine sound. For example, arunning-linked sound (simulated motor sound) simulating an operationsound of an electric motor may be generated, and a different type ofsound from a sound generated by a motor may be generated. Further, therunning-linked sound to be generated is not necessarily of one type, andthe running-linked sound producing device may be configured so as to beable to generate a plurality of types of running-linked soundsselectively.

Moreover, in the foregoing preferred embodiments, basic order sound dataand basic random sound data simulating an order sound component and arandom sound component of an engine (or a vehicle powered by an engine),respectively, are preferably used as first and second component basicsound data. For generating a running-linked sound other than an enginesound or motor sound, it suffices to prepare first component basic sounddata and second component basic sound data accordingly. It then sufficesto change the tone of the first component basic sound data according toa motor rotation speed and keep the tone of the second component basicsound data regardless of the motor rotation speed.

Further, it is not necessary to combine a first component sound such asan order sound and a second component sound such as a random sound so asto synthesize a running-linked sound. A running-linked sound may begenerated, for example, by recording an actual sound (for example, anengine sound or motor sound) to prepare basic sound data, and processingthe basic sound data according to a running state of a vehicle.

Further, in the foregoing preferred embodiments, the running-linkedsound producing device 30 having a configuration of the device main body31 and the speaker 32 being connected by the wiring 33 has beendisclosed, but the device main body 31 and the speaker 32 may beunitary. In this way, wiring between the device main body 31 and thespeaker 32 can also be omitted, so that the configuration is furthersimplified, and fitting work to a vehicle body also becomes easier.

In addition, the preferred embodiments of the present invention can bevariously modified in design within the scope of the matters describedin the claims.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

The invention claimed is:
 1. A running-linked sound producing device forproducing a running-linked sound according to a running state of avehicle, the running-linked sound producing device comprising: a vehiclespeed estimating unit programmed to estimate a vehicle speed of thevehicle using an output signal of at least one sensor provided in therunning-linked sound producing device and without using an output signalfrom a vehicle sensor; an accelerator command value estimating unitprogrammed to estimate an accelerator command value based on the vehiclespeed estimated by the vehicle speed estimating unit; and arunning-linked sound generating unit programmed to generate arunning-linked sound based on the vehicle speed estimated by the vehiclespeed estimating unit and the accelerator command value estimated by theaccelerator command value estimating unit.
 2. A running-linked soundproducing device for producing a running-linked sound according to arunning state of a vehicle, the running-linked sound producing devicecomprising: a vehicle speed estimating unit programmed to estimate avehicle speed of the vehicle; an accelerator command value estimatingunit programmed to estimate an accelerator command value based on thevehicle speed estimated by the vehicle speed estimating unit; and arunning-linked sound generating unit programmed to generate arunning-linked sound based on the vehicle speed estimated by the vehiclespeed estimating unit and the accelerator command value estimated by theaccelerator command value estimating unit; wherein the acceleratorcommand value estimating unit includes a torque estimating unitprogrammed to estimate a producing torque of a motor of the vehiclebased on the vehicle speed estimated by the vehicle speed estimatingunit, and to estimate the accelerator command value according to theestimated producing torque.
 3. The running-linked sound producing deviceaccording to claim 2, wherein the torque estimating unit includes: arunning resistance computing unit programmed to compute a runningresistance of the vehicle; and a necessary torque computing unitprogrammed to compute a necessary torque that needs to be produced bythe motor in order to make the vehicle run based on the runningresistance computed by the running resistance computing unit; whereinthe accelerator command value estimating unit is programmed to estimatethe accelerator command value based on the necessary torque computed bythe necessary torque computing unit and a motor rotation speed.
 4. Therunning-linked sound producing device according to claim 3, furthercomprising: an acceleration computing unit programmed to estimate anacceleration of the vehicle; and a gradient estimating unit programmedto estimate a gradient of a road surface on which the vehicle isrunning; wherein the necessary torque computing unit is programmed tocompute the necessary torque based on the running resistance computed bythe running resistance computing unit, the acceleration estimated by theacceleration computing unit, and the road surface gradient estimated bythe gradient estimating unit.
 5. The running-linked sound producingdevice according to claim 3, wherein the accelerator command valueestimating unit includes: a producing torque ratio computing unitprogrammed to compute a producing torque ratio, the producing torqueratio being a ratio of the necessary torque to a maximum torque that canbe produced by the motor at the motor rotation speed; wherein theaccelerator command value estimating unit is programmed to estimate theaccelerator command value based on the producing torque ratio computedby the producing torque ratio computing unit.
 6. The running-linkedsound producing device according to claim 5, further comprising a motorcharacteristic changing unit programmed to change characteristics of themaximum torque with respect to the motor rotation speed.
 7. Therunning-linked sound producing device according to claim 5, furthercomprising an accelerator characteristic changing unit programmed tochange characteristics of the accelerator command value with respect tothe producing torque ratio.
 8. The running-linked sound producing deviceaccording to claim 2, wherein the vehicle speed estimating unit isprogrammed to estimate the vehicle speed using an output signal of atleast one sensor provided in the running-linked sound producing device.9. The running-linked sound producing device according to claim 8,wherein the at least one sensor includes an acceleration sensor, and thevehicle speed estimating unit is programmed to use an accelerationdetected by the acceleration sensor to estimate the vehicle speed.
 10. Arunning-linked sound producing device for producing a running-linkedsound according to a running state of a vehicle, the running-linkedsound producing device comprising: a vehicle speed estimating unitprogrammed to estimate a vehicle speed of the vehicle; an acceleratorcommand value estimating unit programmed to estimate an acceleratorcommand value based on the vehicle speed estimated by the vehicle speedestimating unit; and a running-linked sound generating unit programmedto generate a running-linked sound based on the vehicle speed estimatedby the vehicle speed estimating unit and the accelerator command valueestimated by the accelerator command value estimating unit; wherein thevehicle speed estimating unit is programmed to estimate the vehiclespeed using an output signal of at least one sensor provided in therunning-linked sound producing device; the at least one sensor includesan acceleration sensor, and the vehicle speed estimating unit isprogrammed to use an acceleration detected by the acceleration sensor toestimate the vehicle speed; the running-linked sound producing devicefurther includes a gradient estimating unit programmed to estimate agradient of a road surface on which the vehicle is running; and thevehicle speed estimating unit is programmed to correct the accelerationdetected by the acceleration sensor according to the road surfacegradient estimated by the gradient estimating unit, and to use thecorrected acceleration to estimate the vehicle speed.
 11. Therunning-linked sound producing device according to claim 10, wherein theat least one sensor includes an angular rate sensor; and the gradientestimating unit is programmed to integrate an angular rate detected bythe angular rate sensor, and to estimate the road surface gradient. 12.The running-linked sound producing device according to claim 8, whereinthe at least one sensor includes a GPS receiver, and the vehicle speedestimating unit is programmed to estimate the vehicle speed based on anoutput signal of the GPS receiver.
 13. The running-linked soundproducing device according to claim 1, wherein the running-linked soundgenerating unit includes a motor rotation speed estimating unitprogrammed to estimate a motor rotation speed based on the vehicle speedestimated by the vehicle speed estimating unit, and to generate therunning-linked sound based on the accelerator command value and themotor rotation speed estimated by the motor rotation speed estimatingunit.
 14. The running-linked sound producing device according to claim1, wherein the running-linked sound generating unit includes a motorrotation speed estimating unit programmed to estimate a motor rotationspeed based on the vehicle speed estimated by the vehicle speedestimating unit and the accelerator command value estimated by theaccelerator command value estimating unit, and to generate therunning-linked sound based on the accelerator command value and themotor rotation speed estimated by the motor rotation speed estimatingunit.